| 摘要 |
442,613. Printing telegraphy. NATIONALE TELEPHON - UND TELEGRAPHENWERKE GES., 136, Mainzerlandstrasse, Frankfort-on-Main, Germany. Oct. 31, 1934, No. 31271. Convention date, Oct. 31, 1933. [Class 40 (iii)] In a double-current system in which the voltage-source of the transmitter at each station is divided into unequal parts B1, B2, Fig. 1, the polarized receiving relays PR at the two stations are permanently in the line and the transmitter contacts sk are brought into circuit by switches Z during the transmission of a message. Thus, no current flows in the line during rest periods, but when switches Z have both been operated so that the transmitters are in circuit through contacts 2, the two 6-volt batteries B1 B<1>1 aid one another so as to apply a 12-volt spacing potential to the line. When transmitter contact sk is marking, however, the 18-volt battery B2 opposes the 6-volt battery B1, so that a 12-volt marking potential is applied to this line. Current may be derived from a potentiometer Pot, Fig. 2, fed by alternating-current mains NA through rectifiers G1 and a filter Dr or from directcurrent mains through a similar filter (part of Fig. 2, not shown). The speed of the printer motor M is controlled by a centrifugal contact F1k, the state of which is indicated by a lamp Gi. Preparation of local circuits. When a key ET of the keyboard is depressed the bar U actuates the pawl K and so causes the distributer SV to be driven by the motor M. At the same time, a contact ek is closed and magnet ZM is energized so that a switch Z, of the kind described in Specifications 420,820 and 420,853, is thrown. This switch closes at 1 the circuit of the motor M (which for economy is fed with unrectified current), brings the transmitter contact sk into circuit with the line at 2, and completes at 4 the circuit of the local receiving relay EM which operates the printer and is controlled by the time relay PR. The signal set up by the combination bars KS on the distributer SV is then sent over the line L by the distributer, which is constructed as described in Specification 389,999, the contact sk being actuated by the distributer cams so as to send the required combinations to line. The first combination comprises five negative impulses to allow for preparation of the receiver circuits. At the receiving station the switch Z is tripped when the start signal, comprising the unopposed 18 volts of battery B2 of the sending station, causes the relay PR to short-circuit the condensers CF and so to energize the magnet ZM. Thereupon switch Z at the receiving station is thrown and the 6 volts of receiving battery B1 is opposed to the 18 volts of sending battery B2. |
